1. Field of the Invention
The present invention relates to a process for preparing a polyoxyalkylene polyamine having a terminal secondary amino group. More particularly, the invention relates to a process for preparing a polyoxyalkylene polyamine having a secondary amino group at the end of a polymer chain by the reaction of a polyoxyalkylene polyol with a primary amine which comprises conducting the reaction by using a catalyst containing (1) Ni and Zn, (2) Co and Zn, or (3) Ni, Co and Zn; by using a catalyst in the presence of a monohydric alcohol; and by using the catalyst containing (1) Ni and Zn, (2) Co and Zn, or (3) Ni, Co and Zn, respectively in the presence of the monohydric alcohol.
The polyoxyalkylene polyamine having amino groups at the end of polymer chain provides a polyurea by addition polymerization with polyisocyanate. Addition polymerization is carried out by processing methods such as reaction injection molding (RIM) to form polyurea base molded articles. The polyoxyalkylene polyamine is useful as a raw material for elastomers, flexible foams, rigid foams and other various plastics such as epoxy resin, polyamide and polyimide.
2. Description of the Prior Art
Processes have been known on the preparation of a polyoxyalkylene polyamine having an amino group at the end of the polymer chain by reacting polyoxyalkylene polyol with ammonia or an amine. For example, Belgium Patent 677124 has proposed a preparation process for reacting a polyoxyalkylene polyol with ammonia at a high temperature under high pressure in the presence of a Raney metal catalyst. In the process, all terminal amines in the resulting polyoxyalkylene polyamine are primary amino groups. The polyoxyalkylene polyamine having primary amino groups at the end of polymer chain has too high reactivity with isocyanate groups. Hence the polyamine has a problem that urea reaction is difficult to control and a special and expensive high-speed machine is required for molding.
On the other hand, a polyoxyalkylene polyamine having secondary amino groups has mild reactivity with isocyanate group as compared with that having primary amino groups. Hence secondary amino groups have a large merit that the urea reaction can be controlled with ease and the molding operation is readily performed. As to the process for preparing the polyoxyalkylene polyamine having secondary amino groups, Japanese Patent Publication No. 7289/1970 discloses a process for reacting a polyalkylene polyol with ammonia or a primary amine at a high temperature under high pressure in the presence of a Raney metal catalyst. When the polyoxyalkylene polyol is reacted with ammonia alone, a polyoxyalkylene polyamine having secondary amino groups is formed by intermolecular reaction. Thus the secondary amino groups obtained are not located at the end of the polymer chain. The high possibility of the intermolecular condensed polyoxyalkylene polyamine is also present in the products prepared by reacting with primary amines. The present inventors have carried out experiments in order to prove the intermolecular condensation. As illustrated in Comparative Example 4 described below, secondary-amine based nitrogen was definitely detected in the products. However, the sum of the total amine value and the unreacted hydroxyl value was much lower than the hydroxyl value of the polyoxyalkylene polyol raw material, which result proved the presence of intermolecular condensed polyoxyalkylene polyamine.
Therefore, the secondary amine obtained by the above process is different in structure and composition from the polyoxyalkylene polyamine of this invention which has secondary amino groups at the end of polymer chain.